Thin film transistor substrate

ABSTRACT

An OLED display device is disclosed, which comprises: a TFT substrate, comprising a substrate and plural TFT units disposed on the substrate; and an OLED unit electrically connected to one of the plural TFT units. The TFT units respectively comprise: an active layer disposed on the substrate and made of polysilicon; a first insulating layer disposed on the active layer; source and drain electrodes disposed on the first insulating layer; a metal layer disposed on the first insulating layer; and a second insulating layer disposed on the metal layer, wherein the metal layer has plural first protrusions at a top surface thereof, the second insulating layer comprises a first region corresponding to the active layer and a second region corresponding to a region outside the active layer, and a roughness of a top surface of the first region is greater than that of the second region.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefits of the Taiwan Patent ApplicationSerial Number 103131121, filed on Sep. 10, 2014, the subject matter ofwhich is incorporated herein by reference.

This application is a continuation (CA) of U.S. Patent application for“THIN FILM TRANSISTOR SUBSTRATE”, U.S. application Ser. No. 14/541,105filed Nov. 13, 2014, and the subject matter of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin film transistor (TFT) substrateand, more particularly, to a TFT substrate which can increase storagecapacities of pixels and contact areas of insulating layers.

2. Description of Related Art

In recent years, all the display devices are developed toward havingsmall volume, thin thickness and light weight as the display techniquesprogresses. Hence, a conventional cathode ray tube (CRT) display isgradually replaced by flat panel display devices such as a liquidcrystal display (LCD) device and an organic light emitting diode (OLED)display device. The flat panel display devices can be applied to variousfields. For example, the daily used devices such as cell phones,notebooks, video cameras, cameras, music players, navigation devices,and televisions are equipped with the flat panel display devices.

Although the LCD device and the OLED display device are commerciallyavailable and especially the techniques for the LCD device are muchmature, every manufacturer is desired to develop display devices withimproved display quality to meet customers' requirement as the displaydevices developed. In particular, the structure of the TFT substrate isone factor related to the display quality.

Even though the LCD device and the OLED display device are welldeveloped and commercialized, it is still necessary to develop a displaydevice with improved display quality to meet the customers' requirement.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a thin film transistor(TFT) substrate, wherein storage capacities in pixels and contact areaof an insulating layer can be increased.

To achieve the object, a first aspect of the present invention providesa thin film transistor substrate comprising: a substrate; and pluralthin film transistor (TFT) units disposed on the substrate andrespectively comprising: an active layer disposed on the substrate andmade of polysilicon; an insulating layer disposed on the active layer;and a source electrode and a drain electrode disposed on the insulatinglayer, wherein the insulating layer comprises a first regioncorresponding to the active layer and a second region corresponding to aregion outside the active layer, and a roughness of the first region islarger than that of the second region.

In the TFT substrate of the first aspect of the present invention, theTFT units may further respectively comprise a metal layer disposed onthe insulating layer and having plural first protrusions.

In the TFT substrate of the first aspect of the present invention, themetal layer has a first thickness, the first protrusions respectivelyhave a first height which is a distance between a top end of the firstprotrusion and an average surface of the metal layer, and the firstheight of the first protrusion may be 10% to 30% of the first thicknessof the metal layer.

In the TFT substrate of the first aspect of the present invention, theinsulating layer may have plural second protrusions.

In the TFT substrate of the first aspect of the present invention, theinsulating layer has a second thickness, the second protrusionsrespectively have a second height which is a distance between a top endof the second protrusion and an average surface of the insulating layer,and the second height of the second protrusions may be 30% to 70% of thesecond thickness of the insulating layer.

In the TFT substrate of the first aspect of the present invention, theinsulating layer may have plural second protrusions, and a part of thefirst protrusions of the metal layer may correspond to the secondprotrusions of the insulating layer.

In the TFT substrate of the first aspect of the present invention, theactive layer has a side, and a curvature of the insulating layercorresponding to the side of the active layer may be smaller than thatof the side thereof.

In addition, a second aspect of the present invention further providesanother TFT substrate, which comprises: a substrate; and plural TFTunits disposed on the substrate and respectively comprising: an activelayer disposed on the substrate and made of polysilicon; an insulatinglayer disposed on the active layer; and a source electrode and a drainelectrode disposed on the insulating layer, wherein the insulating layerhas plural second protrusions.

In the TFT substrate of the second aspect of the present invention, theinsulating layer has a second thickness, the second protrusionsrespectively have a second height which is a distance between a top endof the second protrusion and an average surface of the insulating layer,and the second height of the second protrusions may be 30% to 70% of thesecond thickness of the insulating layer.

In the TFT substrate of the second aspect of the present invention, thethin film transistor units may further respectively comprise a metallayer disposed on the insulating layer and having plural firstprotrusions.

In the TFT substrate of the second aspect of the present invention, themetal layer has a first thickness, the first protrusions respectivelyhave a first height which is a distance between a top end of the firstprotrusion and an average surface of the metal layer, and the firstheight of the first protrusion may be 10% to 30% of the first thicknessof the metal layer.

In the TFT substrate of the second aspect of the present invention, apart of the first protrusions of the metal layer may correspond to thesecond protrusions of the insulating layer.

In the TFT substrate of the second aspect of the present invention, theinsulating layer may comprise a first region corresponding to the activelayer and a second region corresponding to a region outside the activelayer, and a roughness of the first region can be larger than that ofthe second region.

In the TFT substrate of the second aspect of the present invention, theactive layer has a side, and a curvature of the insulating layercorresponding to the side of the active layer may be smaller than thatof the side thereof.

In all the TFT substrate of the first and second aspects of the presentinvention, the surface of the insulating layer is designed to be in alumpy shape with plural second protrusions formed thereon, resulting inthe contact area of the insulating layer to other layers increased.Hence, the adhesion between the insulating layer and other layers can beincreased, and the peeling therebetween can further be prevented. Inaddition, in all the TFT substrate of the first and second aspects ofthe present invention, the surface of the metal layer located on theinsulating layer is further designed to be in a lumpy shape with pluralfirst protrusions formed thereon, resulting in the surface of the metallayer increased. Hence, the metal layer can have increased capacity tofurther increase the storage capacities of pixels.

Other objects, advantages, and novel features of the invention willbecome more apparent from the following detailed description when takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an OLED display device according toone preferred embodiment of the present invention;

FIG. 2 is schematic view showing a layout of an OLED display deviceaccording to one preferred embodiment of the present invention;

FIG. 3 is a cross-sectional view of a TFT substrate of an OLED displaydevice according to one preferred embodiment of the present invention;

FIG. 4 is a cross-sectional view showing a partial TFT substrate of anOLED display device according to one preferred embodiment of the presentinvention; and

FIG. 5 is a cross-sectional view showing a partial TFT substrate of anOLED display device according to one preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention has been described in an illustrative manner, andit is to be understood that the terminology used is intended to be inthe nature of description rather than of limitation. Many modificationsand variations of the present invention are possible in light of theabove teachings. Therefore, it is to be understood that within the scopeof the appended claims, the invention may be practiced otherwise than asspecifically described.

FIG. 1 is a cross-sectional view of an OLED display device according toone preferred embodiment of the present invention. During the processfor manufacturing the OLED display device, a first substrate 11 and asecond substrate 12 are firstly provided. Organic light emitting diode(OLED) units 15 and pixel defining layers 16 are disposed on the firstsubstrate 11, wherein each pixel defining layer 16 is disposed betweentwo adjacent OLED units 15. In addition, plural spacers 14 are disposedon the second substrate 12, and a sealant 13 (a fit sealant in thepresent embodiment) is formed on a periphery of the second substrate 12in advance, which is formed through a dispensing process and a sinteringprocess to be fixed on the second substrate 12. Then, the firstsubstrate 11 is assembled with the second substrate 12, wherein thespacers 14 on the second substrate 12 correspond to regions outside thepixel opening 161 of the pixel defining layer 16. After the sealant 13is adhered onto the first substrate 11 through a laser process, an OLEDdisplay device of the present embodiment is obtained.

In the present embodiment, both the first substrate 11 and the secondsubstrate 12 are glass substrates. In addition, the OLED display deviceof the present embodiment comprises a display region A and a non-displayregion B, wherein the non-display region B is a region with circuitsformed thereon. Furthermore, in the present embodiment, the OLED units15 can respectively emit red, green and blue light; but the presentinvention is not limited thereto. For example, the OLED units 15 can bewhite OLED units, and a color filter unit (not shown in the figure) isfurther disposed on a side of the first substrate 11 or the secondsubstrate 12.

FIG. 2 is a schematic view showing a layout of an OLED display device ofthe present embodiment. As shown in FIG. 2, in the OLED display deviceof the present embodiment, each pixel unit respectively comprises: ascan line, a data line, a capacitor line, a supply line, a switching TFTunit (shown as switching TFT in FIG. 2), a driving TFT unit (shown asdriving TFT in FIG. 2), a storage capacitor, and an OLED unit (shown asOLED in FIG. 2) connecting to a first electrode and a second electrode.

FIG. 3 is a cross-sectional view showing a partial display region of anOLED display device of the present embodiment. As shown in FIGS. 1 and3, the OLED display device of the present embodiment comprises: a firstsubstrate 11 and a second substrate 12 opposite thereto. In the presentembodiment, the TFT units used in the OLED display device are lowtemperature poly-silicon (LTPS) TFT units. As shown in FIG. 3, in thedisplay region A of FIG. 1, a first substrate 11 is firstly provided, abuffer layer 101 is formed thereon, and an active layer 103 is furtherformed on the buffer layer 101. In the present embodiment, the activelayer 103 is made of polysilicon formed by annealing amorphous silicon.Next, a first insulating layer 104, a second insulating layer 105, afirst metal layer 111, a third insulating layer 112 and a fourthinsulating layer 114 are sequentially formed on the first substrate 11.Herein, the first metal layer 111 located in the TFT regions TFT1, TFT2is served as gate electrodes. The first insulating layer 104 and thesecond insulating layer 105 are served as gate insulating layers, whichare made of any insulating material generally used in the art, such assilicon oxides and silicon nitrides. In addition, the third insulatinglayer 112 and the fourth insulating layer 114 can also be made by theaforementioned insulating material generally used in the art. Then, asecond metal layer 116 is formed on the fourth insulating layer 114.Herein, the second metal layer 116 located in the TFT regions TFT1, TFT2further penetrate through the third insulating layer 112 and the fourthinsulating layer 114, and selectively penetrate through the firstinsulating layer 104 and the second insulating layer 105, to be used asa source electrode and a drain electrode electrically connecting to theactive layer 103. After the aforementioned process, the TFT substrate ofthe present embodiment is obtained. In the present embodiment, the TFTsubstrate comprises two TFT regions TFT1, TFT2, wherein the TFT regionTFT1 corresponds to the switching TFT shown in FIG. 2, and the TFTregion TFT2 corresponds to the driving TFT shown in FIG. 2. In addition,in the present embodiment, except for the TFT regions TFT1, TFT2, acapacitor region C is also formed, which corresponds to the storagecapacitor shown in FIG. 2.

As shown in FIGS. 1 and 3, after the TFT substrate is formed, aprotection layer 115, a planer layer 117, a first electrode 151 and apixel defining layer 16 are sequentially formed thereon, wherein thefirst electrode 151 is formed not only on the planer layer 117 but alsoin a planer layer opening 117 a of the planer layer 117 and a protectionlayer opening 115 a of the protection layer 115 to electrically connectto the second metal layer 116. Furthermore, the pixel defining layer 16is also formed with a pixel opening 161. Then, an organic light emittinglayer 152 and a second electrode 153 are sequentially formed on thepixel defining layer 16 and the first electrode 151 as well as in thepixel opening 161 to finish the OLED unit 15 of the present embodiment.Hence, as shown in FIGS. 1 and 3, the OLED unit 15 of the presentembodiment comprises a first electrode 151, an organic light emittinglayer 152 and a second electrode 153 sequentially laminated, and thefirst electrode 151 electrically connects to the second metal layer 116.In addition, the pixel defining layer 16 locates between the firstelectrode 151 and the organic light emitting layer 152, and a lightemitting region is defined by the pixel opening 161 of the pixeldefining layer 16.

In the present embodiment, the first metal layer 111 and the secondmetal layer 116 are used as circuits. For example, as shown in FIG. 3,the first metal layer 111 herein is used as a gate electrode of a TFTunit, and the second metal layer 116 is used as a source electrode and adrain electrode thereof. In addition, the gate electrode and a scan line(not shown in the figure) simultaneously formed by the first metal layer111 electrically connect to each other, and the source and drainelectrodes and a data line (not shown in the figure) simultaneouslyformed by the second metal layer 116 also electrically connect to eachother. In the present embodiment, the first metal layer 111 and thesecond metal layer 116 can be made of any conductive material generallyused in the art, such as metals, alloys, metal oxide, metal oxynitrides,and other electrode materials generally used in the art; and preferablymetals. In the present embodiment, the first metal layer 111 is made ofMo, and the second metal layer 116 is a composite metal layer with a Tilayer, an Al layer and another Ti layer sequentially laminated from aside facing to the first substrate 11. In addition, the protection layer115 is made of any insulating material generally used in the art, suchas silicon oxides and silicon nitrides.

In the present embodiment, the first electrode 151 can be made of anymaterial for reflective electrodes generally used in the art, and thesecond electrode 153 can be made of any material for transparent orsemi-transparent electrodes generally used in the art. The materials forthe reflective electrodes may be Ag, Ge, Al, Cu, Mo, Ti, Sn, AlNd, ACXor APC, the materials for the transparent electrodes may be transparentconductive oxides (TCO) such as ITO and IZO, and the semi-transparentelectrodes may be metal thin film electrodes such as Mg/Ag alloy thinfilm electrodes, Au thin film electrodes, Pt thin film electrodes and Althin film electrodes. In addition, the second electrode 153 used hereincan be a composite electrode of a transparent electrode and asemi-transparent electrode (for example, a composite electrode of a TCOelectrode and a Pt thin film electrode), if it is needed. Herein, onlythe OLED unit comprising the first electrode 151, the organic lightemitting layer 152 and the second electrode 153 is present, but thepresent invention is not limited thereto. Other OLED units generallyused in the art can also be applied to the OLED display panel of thepresent invention, for example, the OLED unit comprising an electrontransporting layer, an electron injection layer, a hole transportinglayer, a hole injection layer, and/or other layers capable offacilitating the combination of holes and electrons.

FIGS. 4 and 5 are cross-sectional views showing a partial TFT substrateof an OLED display device of the present embodiment, which arerespectively enlarge views of the TFT regions TFT1, TFT2 shown in FIG.3. As shown in FIGS. 4 and 5, after the active layer 103 is formed,during the respective processes for forming the first insulating layer104, the second insulating layer 105, the first metal layer 111, thethird insulating layer 112 and the fourth insulating layer 114,patterned masks are used to respectively etch these layers after thelayers are formed by deposition processes known in the art, to make thefirst insulating layer 104, the second insulating layer 105, the firstmetal layer 111, the third insulating layer 112 and the fourthinsulating layer 114 respectively have a lumpy surface having bumps.

More specifically, as shown in FIGS. 4 and 5, the first insulating layer104, the second insulating layer 105, the third insulating layer 112 andthe fourth insulating layer 114 respectively comprise a first region R1corresponding to the active layer 103 and a second region R2corresponding to a region outside the active layer 103, and a roughnessof the first region R1 is larger than that of the second region R2.

In addition, as shown in FIGS. 4 and 5, the first insulating layer 104,the second insulating layer 105, the third insulating layer 112 and thefourth insulating layer 114 respectively have plural second protrusions1041, 1051, 1121, 1141. Herein, a distance between a top end of eachsecond protrusion 1041 and an average surface 104 a of the firstinsulating layer 104 near to the second protrusion 1041, a second heightH2, is respectively 500 nm˜1500 nm; a distance between a top end of eachsecond protrusion 1051 and an average surface 105 a of the secondinsulating layer 105 near to the second protrusion 1051, a second heightH3, is respectively 500 nm˜1500 nm; a distance between a top end of eachsecond protrusion 1121 and an average surface 112 a of the thirdinsulating layer 112 near to the second protrusion 1121, a second heightH4, is respectively 500 nm˜1500 nm; and a distance between a top end ofeach second protrusion 1141 and an average surface 114 a of the fourthinsulating layer 114 near to the second protrusion 1141, a second heightH5, is respectively 500 nm˜1500 nm.

Furthermore, as shown in FIGS. 4 and 5, the first insulating layer 104has a second thickness T2, and the second height H2 of the secondprotrusions 1041 is 30% to 70% of the second thickness T2 of the firstinsulating layer 104; the second insulating layer 105 has a secondthickness T3, and the second height H3 of the second protrusion 1051 is20% to 50% of the second thickness T3 of the second insulating layer105; the third insulating layer 112 has a second thickness T4, and thesecond height H4 of the second protrusion 1121 is 10% to 40% of thesecond thickness T4 of the third insulating layer 112; and the fourthinsulating layer 114 has a second thickness T5, and the second height H5of the second protrusion 1141 is 5% to 30% of the second thickness T5 ofthe fourth insulating layer 114.

As illustrated above, in the TFT substrate of the present invention, thefirst insulating layer, the second insulating layer, the thirdinsulating layer and the fourth insulating layer are designed to havesurfaces present in lumpy shapes having second protrusions formedthereon, and therefore the contact areas of the insulating layers toother layers can be increased. Hence, the adhesions between theinsulating layers and other layers can be improved, and the peelingtherebetween can further be prevented.

In addition, as shown in FIGS. 4 and 5, in the TFT substrate of thepresent embodiment, the first metal layer 111 also has a lumpy surfacewith bumps formed thereon. Herein, the first metal layer 111 may furtherhave plural first protrusions 1111, wherein a distance between a top endof each first protrusion 1111 and an average surface 111 a of the firstmetal layer 111 near to the first protrusions 1111, a first height H1,is respectively 500 nm˜1500 nm. Furthermore, the first metal layer 111has a first thickness T1, the first height H1 of the first protrusion1111 is 10% to 30% of the first thickness T1 of the first metal layer111.

As illustrated above, in the TFT substrate of the present invention, themetal layer is designed to have a surface present in a lumpy shapehaving first protrusions formed thereon, and therefore the area of themetal layer can be increased. Hence, the metal layer can have increasedcapacity to further increase the storage capacities of pixels.

In addition, as shown in FIGS. 4 and 5, positions of the secondprotrusion 1041 of the first insulating layer 104, the second protrusion1051 of the second insulating layer 105, the second protrusion 1121 ofthe third insulating layer 112, the second protrusion 1141 of the fourthinsulating layer 114, and the first protrusion 1111 of the first metallayer 111 can be correspond or not correspond to each other, which canbe adjusted according to device requirements.

Furthermore, as shown in FIGS. 4 and 5, the active layer 103 has a side1032, and an inclined surface 1042 of the first insulating layer 104, aninclined surface 1052 of the second insulating layer 105, an inclinedsurface 1122 of the third insulating layer 112 and an inclined surface1142 of the fourth insulating layer 114 respectively correspond to theside 1032 of the active layer 103. Herein, a curvature of one of theinclined surface 1042, 1052, 1122, 1142 is smaller than that of the side1032 thereof.

In the present invention, the term “average surface” refers to anoptimal surface of the sample, which can be a mean surface obtained froman arithmetic average of the absolute values or a square average of theprofile height deviations from the mean line, recorded within theevaluation length.

The TFT substrate obtained from the aforementioned embodiment of thepresent invention can be applied to an OLED display device as well as aLCD device. In addition, the display device provided by the presentinvention can be applied to any electronic device for displaying images,such as a mobile phone, a notebook, a camera, a video camera, a musicplayer, a navigation system, or a television.

Although the present invention has been explained in relation to itspreferred embodiment, it is to be understood that many other possiblemodifications and variations can be made without departing from thespirit and scope of the invention as hereinafter claimed.

What is claimed is:
 1. An OLED display device, comprising: a thin filmtransistor substrate, comprising: a substrate; and plural thin filmtransistor units disposed on the substrate and respectively comprising:an active layer disposed on the substrate and made of polysilicon; afirst insulating layer disposed on the active layer; a source electrodeand a drain electrode disposed on the first insulating layer; a metallayer disposed on the first insulating layer; and a second insulatinglayer disposed on the metal layer, wherein the metal layer has pluralfirst protrusions at a top surface of the metal layer, the secondinsulating layer comprises a first region corresponding to the activelayer and a second region corresponding to a region outside the activelayer, and a roughness of a top surface of the first region is greaterthan a roughness of a top surface of the second region; an OLED unitelectrically connected to one of the plural thin film transistor units,wherein the OLED unit comprises a first electrode; a pixel defininglayer disposed on the first electrode, wherein the pixel defining layerhas a pixel opening corresponding to the first electrode; and a spacerdisposed on the pixel defining layer and corresponding to a regionoutside the pixel opening.
 2. The OLED display device as claimed inclaim 1, wherein the metal layer has a first thickness, the firstprotrusions respectively have a first height which is a distance betweena top end of the first protrusion and the top surface of the metallayer, and the first height of the first protrusion is 10% to 30% of thefirst thickness of the metal layer.
 3. The OLED display device asclaimed in claim 1, wherein the first insulating layer comprises a thirdregion corresponding to the active layer, and the first insulating layerhas plural second protrusions at a top surface of the third region ofthe first insulating layer.
 4. The OLED display device as claimed inclaim 3, wherein the third region of the first insulating layer has asecond thickness, the second protrusions respectively have a secondheight which is a distance between a top end of the second protrusionand the top surface of the third region of the first insulating layer,and the second height of the second protrusions is 30% to 70% of thesecond thickness of the third region the first insulating layer.
 5. TheOLED display device as claimed in claim 1, wherein the first insulatinglayer comprises a third region, and the first insulating layer hasplural second protrusions at a top surface of the third region, themetal layer has a fourth region, at least a part of the firstprotrusions is disposed in the fourth region, and the fourth regioncorresponds to the third region.
 6. The OLED display device as claimedin claim 1, wherein the active layer has a side, and a curvature of thefirst insulating layer corresponding to the side of the active layer isless than that of the side of the active layer.
 7. The OLED displaydevice as claimed in claim 1, wherein the thin film transistor substratefurther comprises a third insulating layer between the metal layer andthe first insulating layer.
 8. The OLED display device as claimed inclaim 7, wherein a roughness of the third insulating layer correspondingto the active layer is greater than a roughness of the third insulatinglayer corresponding to a region outside the active layer.
 9. The OLEDdisplay device as claimed in claim 1, wherein the thin film transistorsubstrate further comprises a fourth insulating layer disposed on thesecond insulating layer.
 10. The OLED display device as claimed in claim9, wherein a roughness of the fourth insulating layer corresponding tothe active layer is greater than a roughness of the fourth insulatinglayer corresponding to a region outside the active layer.
 11. The OLEDdisplay device as claimed in claim 1, wherein the first electrode isconnected to the source electrode or the drain electrode of the one ofthe plural thin film transistor units.
 12. An electronic device,comprising: a thin film transistor substrate, comprising: a substrate;and plural thin film transistor units disposed on the substrate andrespectively comprising: an active layer disposed on the substrate andmade of polysilicon; a first insulating layer disposed on the activelayer; a source electrode and a drain electrode disposed on the firstinsulating layer; a metal layer disposed on the first insulating layer;and a second insulating layer disposed on the metal layer, wherein themetal layer has plural first protrusions at a top surface of the metallayer, the second insulating layer comprises a first regioncorresponding to the active layer and a second region corresponding to aregion outside the active layer, and a roughness of a top surface of thefirst region is greater than a roughness of a top surface of the secondregion; an OLED unit electrically connected to one of the plural thinfilm transistor units, wherein the OLED unit comprises a firstelectrode; a pixel defining layer disposed on the first electrode,wherein the pixel defining layer has a pixel opening corresponding tothe first electrode; and a spacer disposed on the pixel defining layerand corresponding to a region outside the pixel opening.
 13. Theelectronic device as claimed in claim 12, wherein the first insulatinglayer comprises a third region corresponding to the active layer, andthe first insulating layer has plural second protrusions at a topsurface of the third region of the first insulating layer.
 14. Theelectronic device as claimed in claim 12, wherein the first insulatinglayer comprises a third region, and the first insulating layer hasplural second protrusions at a top surface of the third region, themetal layer has a fourth region, at least a part of the firstprotrusions is disposed in the fourth region, and the fourth regioncorresponds to the third region.
 15. The electronic device as claimed inclaim 12, wherein the active layer has a side, and a curvature of thefirst insulating layer corresponding to the side of the active layer isless than that of the side of the active layer.
 16. The electronicdevice as claimed in claim 12, wherein the thin film transistorsubstrate further comprises a third insulating layer between the metallayer and the first insulating layer.
 17. The electronic device asclaimed in claim 16, wherein a roughness of the third insulating layercorresponding to the active layer is greater than a roughness of thethird insulating layer corresponding to a region outside the activelayer.
 18. The electronic device as claimed in claim 12, wherein thethin film transistor substrate further comprises a fourth insulatinglayer disposed on the second insulating layer.
 19. The electronic deviceas claimed in claim 18, wherein a roughness of the fourth insulatinglayer corresponding to the active layer is greater than a roughness ofthe fourth insulating layer corresponding to a region outside the activelayer.
 20. The electronic device as claimed in claim 12, wherein thefirst electrode is connected to the source electrode or the drainelectrode of the one of the plural thin film transistor units.